In a conventional apparatus used for chemical-mechanical polishing of substrates, a substrate holding apparatus is used to hold a substrate and press it against a polishing surface. To prevent the substrate from becoming displaced from the substrate holding apparatus during a polishing operation, a retainer ring is provided around the substrate.
To perform consistent polishing of a substrate surface, it is preferable to maintain the retainer ring in a fixed position facing the polishing surface. However, in the conventional art, the retainer ring comes into contact with the polishing surface during a polishing operation, and is therefore subject to frictional wear. As polishing progresses an amount of frictional wear of the ring increases, which makes it difficult to maintain the ring in a desired fixed position relative to the polishing surface.